[gtk+] mir: don't warn if transient_for is NULL

[William Hua <williamhua src gnome org>]

commit 064f28fcbc54c7254e36d2a2e9b2771ce754f988
Author: William Hua <william hua canonical com>
Date:   Thu Jul 9 15:59:29 2015 -0400

    mir: don't warn if transient_for is NULL

 gdk/mir/gdkmirwindowimpl.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)
---
diff --git a/gdk/mir/gdkmirwindowimpl.c b/gdk/mir/gdkmirwindowimpl.c
index 16035a0..25e57c6 100644
--- a/gdk/mir/gdkmirwindowimpl.c
+++ b/gdk/mir/gdkmirwindowimpl.c
@@ -871,8 +871,6 @@ gdk_mir_window_impl_set_transient_for (GdkWindow *window,
   if (impl->transient_for == parent)
     return;
 
-  g_return_if_fail (impl->transient_for == NULL);
-
   /* Link this window to the parent */
   impl->transient_for = parent;
 }